libpod: add (*Container).ResolvePath()

Add an API to libpod to resolve a path on the container.  We can
refactor the code that was originally written for copy.  Other
functions are requiring a proper path resolution, so libpod seems
like a reasonable home for sharing that code.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/libpod/container_api.go b/libpod/container_api.go
index 0d62a2dd7..951227a4f 100644
--- a/libpod/container_api.go
+++ b/libpod/container_api.go
@@ -776,3 +776,32 @@ func (c *Container) ShouldRestart(ctx context.Context) bool {
 	}
 	return c.shouldRestart()
 }
+
+// ResolvePath resolves the specified path on the root for the container.  The
+// root must either be the mounted image of the container or the already
+// mounted container storage.
+//
+// It returns the resolved root and the resolved path.  Note that the path may
+// resolve to the container's mount point or to a volume or bind mount.
+func (c *Container) ResolvePath(ctx context.Context, root string, path string) (string, string, error) {
+	logrus.Debugf("Resolving path %q (root %q) on container %s", path, root, c.ID())
+
+	// Minimal sanity checks.
+	if len(root)*len(path) == 0 {
+		return "", "", errors.Wrapf(define.ErrInternal, "ResolvePath: root (%q) and path (%q) must be non empty", root, path)
+	}
+	if _, err := os.Stat(root); err != nil {
+		return "", "", errors.Wrapf(err, "cannot locate root to resolve path on container %s", c.ID())
+	}
+
+	if !c.batched {
+		c.lock.Lock()
+		defer c.lock.Unlock()
+
+		if err := c.syncContainer(); err != nil {
+			return "", "", err
+		}
+	}
+
+	return c.resolvePath(root, path)
+}